Athletic playing fields such as football and soccer fields or running tracks are typically provided with a drainage channel system formed alongside the playing surface for receiving and collecting liquid runoff. In particular, running track surfaces may include a polymeric surface which is substantially impervious, making adequate drainage very important. Artificial and natural turf playing surfaces are generally more porous than a running track and may include other drainage systems thereunder, but a drainage channel along the edge of the playing surface may nevertheless be important for draining excess runoff.
For outdoor athletic facilities, a drainage channel system is mainly used for draining rainwater. However, a drainage channel system may also be important in indoor or covered athletic facilities for draining other liquids such as water or solvents used to clean the athletic surface. In either instance, the particular athletic surface may be slightly crowned or sloped from the center to the edges to ensure proper drainage thereof.
A drainage channel system typically includes an elongate and substantially continuous drainage channel extending around the periphery of the athletic surface. The drainage channel may be positioned along the border between athletic surfaces of different types. For example, the drainage channel may be located between a polymeric running track and an artificial turf or natural grass playing field. In addition, the drainage channel may be slightly sloped to enhance flow within the channel. Further, one or more catch basins may be positioned along the channel to collect solid debris and to pass the liquid to effluent pipes for removal from the playing field.
An elongate grate is typically provided over the drainage channel. The elongate grate covers the open top of the channel in order to prevent people from unwittingly stepping into the open channel and/or to prevent relatively large objects from entering the channel and partially blocking the flow of liquid therethrough.
The drainage channel is typically formed from a series of discrete drainage channel sections. A first step in installing such a drainage channel is placing the drainage channel sections in an end-to-end relationship at the proper depth below the desired level of the athletic playing surface. In this regard, a trench may be formed to the desired depth adjacent to the playing surface for receiving the channel sections. Alternatively, the entire area below the athletic playing surface may be graded to the desired depth and various subsurface layers can then be placed thereon, as discussed below.
The adjacent ends of two adjoining drainage channel sections may have interlocking end surfaces and may be supported on a single support brick which has been aligned and secured before placement of the drainage channel sections. It is important that the channel sections be supported in such a manner that the channel sections are precisely aligned so as to ensure proper drainage, to permit the grate to seat properly over the open top of the drainage channel and to prevent adjoining channel sections from being misaligned so as to create a potential trip hazard for athletes or others who pass thereby. This proper alignment of the drainage channel sections can be thwarted even if the support bricks are properly aligned, however, if the drainage channel sections and, more particularly, the respective lower surfaces of the drainage channel sections which are seated upon the support bricks are not properly formed in a predetermined aligned relationship. Once the adjoining drainage channel sections have been interlocked, however, the adjacent ends of the sections may be sealed with an adhesive or sealant to prevent leakage.
Once the drainage channel sections are interlocked in an end-to-end relationship, the lower portions of the drainage channel sections are typically encased in concrete so as to secure the channel. Depending on the type of the desired athletic playing surface, various other subsurface and surface layers are formed over the encasement concrete and the surrounding areas to build up the surface to the desired elevation. For example, after the encasement concrete has been poured, a rock or gravel subsurface layer may be formed thereon.
One or more of these subsurface layers may need to be compressed, such as by tamping, in order to reduce subsequent settling. If improperly applied, it has been found that the compression forces could damage the draining channel. For example, vibratory tamping or rolling machinery could fracture or otherwise damage the sidewalls or bottom wall of the drainage channel, thereby weakening the drainage channel or causing it to leak or collapse.
Upon the compressed gravel layer, an asphalt layer is typically formed. For running track surfaces, a relatively thick asphalt layer is applied so as to allow the uppermost surface of the relatively thin polymeric running track surface which is formed thereover to be at the desired horizontal elevation. For artificial turf surfaces, the underlying asphalt layer may be thinner and may be covered with a layer of cushioning foam such that the overlying artificial turf surface is at the desired level. Alternatively, for artificial turf surfaces, the asphalt and foam layers may be replaced by a resilient elastic layer, also known as an "E-layer", which is formed of discrete rubber particles held together in a binder.
Since the surface layers, such as the artificial turf surface or the running track surface, typically have a predetermined thickness, it is important that the subsurface layers are applied to the proper elevation relative to the drainage channel so that the uppermost exposed surface of the playing surface is located at the desired elevation. This accurate positioning of the playing surfaces is particularly important adjacent a drainage channel or another playing surface since any vertical misalignment between the playing surfaces or the drain channel may create a trip hazard for athletes or others and may create impediment for wheeled vehicles passing thereover.
Prior attempts at providing a suitable drainage channel include a drainage system commercially available under the trademark Aco Sport.RTM. from Aco Polymer Products, Inc. to border natural grass surfaces, artificial turf surfaces and/or running track surfaces. The Aco Sport.RTM. system includes a number of drainage channel configurations which, in some embodiments, are covered by a variety of grates and/or a polymer concrete hard cover. A number of the Aco Sport.RTM. drainage systems include a border or curb formed of ethylene-propylene diene monomer ("EPDM") which delineates the boundary between the adjacent athletic surfaces. Due to the upwardly extending EPDM border, athletes or others must step over the EPDM border to pass over the EPDM border and between the adjacent athletic surfaces. In addition, athletic surfaces which border the Aco Sport.RTM. drainage system are also typically at different elevations so as to create an additional barrier to passing between the athletic playing surfaces.
U.S. Pat. No. 3,433,137 to Henderson also describes a drainage system for securing edge portions of an artificial turf playing surface and for providing drainage for the artificial turf surface. The drainage system includes a U-shaped member having a number of interiorly projecting finger-like elements which retain corresponding straps attached to the inner edge of the artificial turf playing surface. The U-shaped member, which may be formed of sheet steel, includes flanged edge portions which may be covered by a layer of resilient material to provide a semi-firm shoulder which is flush with the surface of the adjacent soil.
U.S. Pat. No. 4,553,874 to Thomann, et al. describes another type of drainage system. In particular, Thomann, et al. discloses a slotted grate intended to fit within a preformed cast drainage channel section. The channel section includes a drainage channel body and a cast frame supported thereon for supporting the channel grate. The channel body may be manufactured of polymer concrete and is provided with protrusions on each side to firmly anchor the drainage channel body within a concrete foundation, which encases most of the channel body. Guide tabs on the cast frame intermesh with a pavement layer which may be formed over the concrete.
As described above, several drainage systems, including the Aco Sport.RTM. drainage system, have been developed which border athletic playing surfaces in order to receive runoff therefrom. However, these drainage systems still do not fully address the needs of modern athletic playing surfaces. For example, at least some of these prior drainage systems do not maintain the athletic playing surfaces which are adjacent to the opposed sides of the drainage channel in a level orientation in order permit athletes and others to more readily pass thereover. In addition, the prior drainage systems do not include means for insuring that the subsurface layers are formed to the proper elevation or means for preventing unnecessary damage to the drainage channel sections during compaction of the subsurface layers.